Electrical resistance element



F. M. GODDARD. ELECTHCAL RESISTANCE ELEMENT. APPLiCATION FILED MAR I2,1920.

1 ,356, 6 1 7. Patented Oct. 26, 1920.

//7 venfor: fFeder/ck M. Goddard.

w g, AX/ZQW UNITED STATES,

PATENT OFFICE.

FREDERICK H. GODDARD, OF BROOKLYN, NEW YORK. ASSIGNOR- TO WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y.. A CORPOM- TI'ON OFNEW YORK.

ELECTRICAL RESISTANCE ELEMENT.

Application filed March 12, 1920.

7 '0 all 'w/mm 1'2. may concern:

Be it known that I Fnnonmon M. Gonnann, a citizen of the l nited States,residing at Brooklyn, in the county of Kings, State of New York, haveinvented certain new and useful Improvements in Electrical ResistanceElements, of which the following is a full, clear, concise, and exactdescription.

This invention relates generally to electrical resistance elements andmore particularly to mountin s for resistance elements.

he object of t e invention is to provide a mounting fora resistanceelement of the crystal type which shall maintain under all conditions aerfect contact between the ole ments thereol A further object of theinvention is to provide a mounting for a or stal such that the crystalmay be used as a i'lateral conductor of variable resistance.

Crystals such as carborundum have the property of varying in electricalresistance to a degree reatly out of proportion to the voltage applied.Experiments show, for example, that with a change of voltage from one totwenty-one volts, the resistance changes from (3660 ohms to 50 ohms.Professor (l. lV. Pierce in his text book entitled Principles ofWireless Telegraph publishcd in 1910, describes, on pages 168 and 169,experiments showing the action of a carborundum crystal when makingrelatively oogl conducting contact with two electrodes. 'lhe resultsshow that under such conditions the crystal is a bilateral conductor,the resistances lielng approximately equalin both di'rectio s.

This nvention is particularly useful in systems such as that describedin Boy D. (onway application Serial No. 224,975. filed March 27, 918. Itis also useful when eon ncctcd in shunt with a telephone receiver toshunt com 'iaratively large currents clue to ringing currents, switchingand the like. So used it is practically opaque to voice currents andinsures the listener against loud l'cceiver clicks, ringing in thereceiver, and the like.

lu accordance with the invention in its preferred form good electricalcontact is made with the carhorundurn or other suitable crystal byemheddin one end of the crystal in a mass of fusih e metal and immersingthe other end in mercury bath.

Specification of Letters Patent.

-tainer 5.

lulcnicd Oct. 26. H120.

Serial No. 385.266.

Insulating material prevents the fusible metal from contacting with themercury. The mercury and the fusible metal form the two electrodes forconnection in a circuit.

The invention in its preferred embodimeat, is shown in the drawing inwhich por tions are cut away to show the internal structure.

A carborundum crystal 1 is held in a on .i 9 of brass or'otherconductive material by means of a mass of fusible metal *2. The fusiblemetal used for the purpose is prefer ably type metal which on coolingerg-ands to ri p the crystal firmly. The on p 3 is provided with acylindrica projection 4.

A glass container 5 its over the cup A washer 13 of insulating materialfits about the projection and extends beyond the cup 3 so as to supfiortboth the on 3 and the concontainer 5 by means of an insulating coment 6inserted into the container 5 through the aperture 8. The cement 6serves not only to hold the cup 3 but to cover the surface thereof andof the fusible metal 2 A portion of the crystal 1 is left exposed andprotruding above the cement layer. Tho maining space within thecontainer 5 is almost entirely filled with a li aid 7. Men cury, being agood electrics conductor, chemically stable and not volatile, is preferred for this purpose. The space 14 is left to allow the mercury toexpand with the temperature without bursting the container 5. a

cylindrical casin 10 made of conductive material prefera. v1y brass, isprovided with a thread 12, somewhat likethat of an incandescent lampbase. The lower endlli is turned in so that when the vessel, 5 is placedIn the casing 10 the washer '13 fits snu ly against it.

no leg of the L shaped iron rod 9 pro jeots through the aperture 8 inthe vessel 5 and dips into the mercury bath-7. The other leg of the rod9 extends through the aperture 16 and is soldered to the oasm I 10.

The space between the ,vessel 5 an the casing 10 is filled with a cement11 which also sealscthe aperture 8 and holds the structure solidlytogether.

Am unt nfr 's thtls provided in which there is a minimuih danger ofbreakage, and

he cup 3 is held firmly in the iii lot;

which is unaffected by vibration or the position in which it is mounted.

What is claimed is:

1. A variable resistance element comprising conducting crystal, ametallic sup orting member for said crystal, a mercury ath for saidcrystal making relatively good contact therewith. and insulatin meansseparating said supporting memoer from said mercury bath.

, 2. A variable resistance element comprising conducting crystal, ametallic supporting member for said crystal, 9, mercur bath makingrelatively good contact wit said crystal, insulating means separatingsaid mercury both from said supporting member, a container for inclosingsaid mercury bath and said supporting member, means for hermeticallysealing the said cup within the said container, external terminals, andconductor means connectin said mercury bath and said cup respective ywith said external terminals.

3. A bilateral variable resistance element colnprising an activecrystal, a metallic supporting cup for said crystal, fusible metal meansfor supporting said crystal in said cup, 3 mei-rnry bath makingrelatively good Contact with said crystal, insulating means separating:said mercury bath from said cup and said fusible metal means, acontainer for inclosing said mercury bath and said cup means forhermetically seal inn the said cup within the said container, externalterminals, and conductor means connecting said mercury bath and said onp respectively with said external terminals.

4. A bilateral variable resistance element comprising a casing ofconductive material, a screw thread pressed therein, a containerinclosed in said casing, said container being open at the bottom andprovided with an apertureat the top a cup within said container, saidcup being of conductive ma terial and provided with a projecting portionprotrudigog through said casing, an e l fys i fusi e m te! were or sunortin said crystal, 1: layeref -insuiating cement covering said cup andsaidlfusihle metal mans and: sealing said on Within said container, aconducting rot projecting thi'ougl'i the aperture in the container andfastened to said casi-n ail messyqi liquid substantial? filling t aremaining" space within sai container, a do a composition sealing ai conainer within said casing.

5. bilateral variable resistance element comprising a cup, an activecrystal supported by the cup, a liquid bath in which a portion of thecrystal 1S submersed, a 0011- tainer in which the liquid bath and thesaid cup are contained, a casing inclosing the container, a compositionfor sealing 131 1.6 said container within the said casing,'terminnlmeans for connecting the resistance element in a circuit and conductormeans for cone necting said mercury bath and said cup,

comprising a supportingmeriiber an active crystal supported hy.,,thesupporting them her. a mem foam 's'ubmersing; a snbst'iin} tinl portion.of the saidcrystal a conthlner in which the mercury bath and said supporting member are containedf an insulatinp: composition for separatingthe said mercury bath from the said si'ipporting member, and'forisealingQthe supporting member within seid container, a "(seeininclosing the maintainer, "a compesiuonflor hermetically sealing thecontainer within the casing, externui'terininai means for connectingtheelement in a hirouft, and ntima e mains conpieicting saiti 1' il'i em nan a is i fisherss eecw1y,' miennieiigiiieiiiiens? In witness whereof, I'herenn'to subscribe my name thislflth (in of Mar h 1 920.

FREnnn cut/r co'nosan, a

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